Prediction and Comparison of Creep Behavior of X20 Steam Plant Piping Network with Different Phenomenological Creep Mode
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JMEPEG https://doi.org/10.1007/s11665-020-05235-5
Prediction and Comparison of Creep Behavior of X20 Steam Plant Piping Network with Different Phenomenological Creep Models Smith Salifu
, Dawood Desai, and Schalk Kok
Submitted: 25 March 2020 / Revised: 16 June 2020 / Accepted: 24 September 2020 In service, steam pipes are subjected to high temperature close to 0.4 Tm (melting temperature) or higher and pressure; thus, making them prone to failure due to creep. Often, the design methods for these steam pipes usually do not provide their specific in-service life; hence, some type of service fitness tests are performed, and data obtained from the tests are used to inform the routine inspections. Choosing a creep model that favorably describe the creep behavior of components in service is paramount to engineers as well as the plant operators. Reports have shown that there are several creep models available and they all behave differently with different materials, and operating conditions. In this study, the creep behavior of X20 (12Cr-1MoVNi) steam piping network subjected to three phenomenological creep models (conventional hyperbolic sine creep, modified hyperbolic sine creep and constitutive creep model) was investigated. Fortran user subroutine scripts were developed for the three models and implemented in finite element (FE) code, Abaqus to determine the creep stress and strain rate, while the useful creep life and creep damage was determined using fe-safe/TURBOlife software. The results show that the modified hyperbolic sine creep model is more suitable for estimating the creep behavior of X20 steam piping under the specified operating conditions because of its more conservative prediction. Keywords
Abaqus, creep rate, creep models, fe-safe/TURBOlife, intrados, loglife, X20
1. Introduction Creep failure is a major concern for high-temperature components and structures in power generation plants (Ref 1, 2). The unplanned failure of these components represents the reality of the power generation plants as the increasing demand for energy has posed enormous pressure on the components in the form of an increase in operating conditions such as temperature and pressure. Hence, the determination of the useful creep life/behavior of power generation plantÕs components particularly, the steam pipes has been a foremost issue due to its direct link to safety and economy (Ref 3). X20 steel (12Cr-1MoVNi) is widely used for making components such as steam pipes and turbine blades that are subjected to operation in the creep regime due to its excellent corrosion and heat resistance (Ref 4, 5). Over the years, the X20 piping systems have been inspected and re-inspected using the replica method, and the result of the inspection was used to study the service performance of the steel. As a complement to this inspection technique, finite element method (FEM) has been used successfully to gain a
Smith Salifu and Dawood Desai, Department of Mechanical and Automation Engineering, Tshwane University of Technology, Pretoria, South Africa;
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